Conventionally, a printing system called a common UNIX (registered trademark) printing system (CUPS) is employed in a computer mounting a UNIX (registered trademark) like OS (refer to “CUPS: Common Unix Printing System using the new generation printing system”, first edition, Piason Education Co. Ltd., Aug. 20, 2002, written by Michael R. Sweet, translated by Oki Data CUPS project).
In this CUPS, a plurality of processes operating on a computer cooperate to perform the data processings in succession to send the image data from the computer to an image processing device. For example, when the print data is outputted from an application process, its print data is sent through a CUPS LPR command process, a CUPS spool system and a CUPS back end process to a printer or a facsimile apparatus that is the image processing device.